a(n) = (n+1)*(2*n)!/2^n.A132911a(n) = (n+1)*(2*n)!/2^n.Terms a(0) =1a(1) =2a(2) =18a(3) =360a(4) =12600a(5) =680400a(6) =52390800a(7) =5448643200a(8) =735566832000External referencesoeis: A132911